Emulsion vehicle for poorly soluble drugs

ABSTRACT

An emulsion of α-tocopherol, stabilized by biocompatible surfactants, as a vehicle or carrier for therapeutic drugs, which is substantially ethanol free and which can be administered to animals or humans various routes is disclosed. Also included in the emulsion is PEGylated vitamin E. PEGylated α-tocopherol includes polyethylene glycol subunits attached by a succinic acid diester at the ring hydroxyl of vitamin E and serves as a primary surfactant, stabilizer and a secondary solvent in emulsions of α-tocopherol.

RELATED APPLICATIONS

[0001] This application is a non-provisional application based on U.S.Provisional Application No. 60/034,188 filed Jan. 7, 1997 and U.S.Provisional Application No. 60/048,840 filed Jun. 6, 1997.

BACKGROUND OF THE INVENTION

[0002] Hundreds of medically useful compounds are discovered each year,but clinical use of these drugs is possible only if a drug deliveryvehicle is developed to transport them to their therapeutic target inthe human body. This problem is particularly critical for drugsrequiring intravenous injection in order to reach their therapeutictarget or dosage but which are water insoluble or poorly water soluble.For such hydrophobic compounds, direct injection may be impossible orhighly dangerous, and can result in hemolysis, phlebitis,hypersensitivity, organ failure and/or death. Such compounds are termedby pharmacists “lipophilic”, “hydrophobic”, or in their most difficultform, “amphiphobic”.

[0003] A few examples of therapeutic substances in these categories areibuprofen, diazepam, griseofulvin, cyclosporin, cortisone, proleukin,etoposide and paclitaxel. Kagkadis, K A et al. (1996) PDA J Pharm SciTech 50(5):317-323; Dardel, O. 1976. Anaesth Scand 20:221-24. Sweetana,S and M J U Akers. (1996) PDA J Pharm Sci Tech 50(5):330-342.

[0004] Administration of chemotherapeutic or anti-cancer agents isparticularly problematic. Low solubility anti-cancer agents aredifficult to solubilize and supply at therapeutically useful levels. Onthe other hand, water-soluble anti-cancer agents are generally taken upby both cancer and non-cancer cells thereby exhibiting non-specificity.

[0005] Efforts to improve water-solubility and comfort of administrationof such agents have not solved, and may have worsened, the twofundamental problems of cancer chemotherapy: 1) non-specific toxicityand 2) rapid clearance form the bloodstream by non-specific mechanisms.In the case of cytotoxins, which form the majority of currentlyavailable chemotherapies, these two problems are clearly related.Whenever the therapeutic is taken up by noncancerous cells, a diminishedamount of the drug remains available to treat the cancer, and moreimportantly, the normal cell ingesting the drug is killed.

[0006] To be effective in treating cancer, the chemotherapeutic must bepresent throughout the affected tissue(s) at high concentration for asustained period of time so that it may be taken up by the cancer cells,but not at so high a concentration that normal cells are injured beyondrepair. Obviously, water soluble molecules can be administered in thisway, but only by slow, continuous infusion and monitoring, aspects whichentail great difficulty, expense and inconvenience.

[0007] A more effective method of administering a cancer therapeutic,particularly a cytotoxin, is in the form of a dispersion of oil in whichthe drug is dissolved. These oily particles are made electricallyneutral and coated in such a way that they do not interact with plasmaproteins and are not trapped by the reticuloendothelial system (RES),instead remaining intact in the tissue or blood for hours, days or evenweeks. In most cases, it is desirable if the particles also distributethemselves into the surrounding lymph nodes which are injected at thesite of a cancer. Nakamoto, Y et al. (1975) Chem Pharm Bull23(10):2232-2238. Takahashi, T et al. (1977) Tohoku J Exp Med123:235-246. In many cases direct injection into blood is the route ofchoice for administration. Even more preferable, following intravenousinjection, the blood-borne particles may be preferentially captured andingested by the cancer cells themselves. An added advantage of aparticulate emulsion for the delivery of a chemotherapeutic is thewidespread property of surfactants used in emulsions to overcomemultidrug resistance.

[0008] For drugs that cannot be formulated as an aqueous solution,emulsions have typically been most cost-effective and gentle toadminister, although there have been serious problems with making themsterile and endotoxin free so that they may be administered byintravenous injection. The oils typically used for pharmaceuticalemulsions include saponifiable oils from the family of triglycerides,for example, soybean oil, sesame seed oil, cottonseed oil, safflower oiland the like. Hansrani, P K et al., (1983) J Parenter Sci Technol37:145-150. One or more surfactants are used to stabilize the emulsion,and excipients are added to render the emulsion more biocompatible,stable and less toxic. Lecithin from egg yolks or soybeans is a commonlyused surfactant. Sterile manufacturing can be accomplished by absolutesterilization of all the components before manufacture, followed byabsolutely aseptic technique in all stages of manufacture. However,improved ease of manufacture and assurance of sterility is obtained byterminal sterilization following sanitary manufacture, either by heat orby filtration. Unfortunately, not all emulsions are suitable for heat orfiltration treatments.

[0009] Stability has been shown to be influenced by the size andhomogeneity of the emulsion. The preferred emulsion consists of asuspension of sub-micron particles, with a mean size of no greater than200 nanometers. A stable dispersion in this size range is not easilyachieved, but has the benefit that it is expected to circulate longer inthe bloodstream. Further, less of the stable dispersion is phagocytizednon-specifically by the reticuloendothelial system. As a result the drugis more likely to reach its therapeutic target. Thus, a preferred drugemulsion will be designed to be actively taken up by the target cell ororgan, and is targeted away from the RES.

[0010] The use of vitamin E in emulsions is known. In addition to thehundreds of examples where vitamin E in small quantities [for example,less than 1%, R T Lyons. Pharm Res 13(9): S-226, (1996) “Formulationdevelopment of an injectable oil-in-water emulsion containing thelipophilic antioxidants K-tocopherol and P-carotene”] is used as ananti-oxidant in emulsions, the first primitive, injectable vitamin Eemulsions per se were made by Hidiroglou for dietary supplementation insheep and for research on the pharmacokinetics of vitamin E and itsderivatives. Hidiroglou M and Karpinski K. (1988) Brit J Nutrit59:509-518.

[0011] For mice, an injectable form of vitamin E was prepared by Katoand coworkers. Kato Y., et al. (1993) Chem Pharm Bull 41(3):599-604.Micellar solutions were formulated with Tween 80, Brij 58 and HCO-60.Isopropanol was used as a co-solvent, and was then removed by vacuumevaporation; the residual oil glass was then taken up in water withvortexing as a micellar suspension. An emulsion was also prepared bydissolving vitamin E with soy phosphatidycholine (lecithin) and soybeanoil. Water was added and the emulsion prepared with sonication.

[0012] In 1983, E-Ferol, a vitamin E emulsion was introduced for vitaminE supplementation and therapy in neonates. Alade S L et al. (1986)Pediatrics 77(4):593-597. Within a few months over 30 babies had died asa result of receiving the product, and the product was promptlywithdrawn by FDA order. The surfactant mixture used in E-Ferol toemulsify 25 mg/mL vitamin E consisted of 9% Tween 80 and 1% Tween 20.These surfactants seem ultimately to have been responsible for theunfortunate deaths. This experience illustrates the need for improvedformulations and the importance of selecting suitable biocompatiblesurfactants and carefully monitoring their levels in parenteralemulsions and.

[0013] An alternative means of solubilizing low solubility compounds isdirect solubilization in a non-aqueous milieu, for example alcohol (suchas ethanol) dimethylsulfoxide or triacetin. An example in PCTapplication WO 95/11039 describes the use of vitamin E and the vitamin Ederivative TPGS in combination with ethanol and the immuno-suppressantmolecule cyclosporin. Alcohol-containing solutions can be administeredwith care, but are typically given by intravenous drip to avoid thepain, vascular irritation and toxicity associated with bolus injectionof these solutions.

[0014] Problems with pharmaceutical formulations in non-aqueous solventsand solubilizers such as alcohol (ethanol, isopropanol, benzyl alcohol,etc.) relate to the ability of these solvents to extract toxicsubstances, for example plasticizers, from their containers. The currentcommercial formulation for the anti-cancer drug paclitaxel, for example,consists of a mixture of hydroxylated castor oil and ethanol, andrapidly extracts plasticizers such as di-(2-ethylhexyl)-phthalate fromcommonly used intravenous infusion tubing and bags. Adverse reactions tothe plasticizers have been reported, such as respiratory distress,necessitating the use of special infusion systems at extra expense andtime. Waugh, et al. (1991) Am J Hosp Pharmacists 48:1520.

[0015] In light of these problems, it can be seen that the idealemulsion vehicle would be inexpensive, non-irritating or even nutritiveand palliative in itself, terminally sterilizable by either heat orfiltration, stable for at least 1 year under controlled storageconditions, accommodate a wide variety of water insoluble and poorlysoluble drugs and be substantially ethanol-free. In addition to thosedrugs which are lipophilic and dissolve in oils, also needed is avehicle which will stabilize, and carry in the form of an emulsion,drugs which are poorly soluble in lipids and in water.

SUMMARY OF THE INVENTION

[0016] In order to meet these needs, the present invention is directedto pharmaceutical compositions including: α-tocopherol, a surfactant ormixtures of surfactants, with and without an aqueous phase, and atherapeutic agent wherein the composition is in the form of an emulsion,micellar solution or a self-emulsifying drug delivery system. In apreferred form, the solution is substantially ethanol-free.

[0017] The pharmaceutical compositions can be stabilized by the additionof various amphiphilic molecules, including anionic, nonionic, cationic,and zwitterionic surfactants. Preferably, these molecules are PEGylatedsurfactants and optimally PEGylated α-tocopherol.

[0018] The amphiphilic molecules further include surfactants such asascorbyl-6 palmitate; stearylamine; sucrose fatty acid esters, variousvitamin E derivatives and fluorine-containing surfactants, such as theZonyl brand series and a polyoxypropylene-polyoxyethylene glycolnonionic block copolymer.

[0019] The therapeutic agent of the emulsion may be a chemotherapeuticagent preferably a taxoid analog and most preferably, paclitaxel.

[0020] The emulsions of the invention can comprise an aqueous mediumwhen in the form of an emulsion or micellar solution. This medium cancontain various additives to assist in stabilizing the emulsion or inrendering the formulation biocompatible.

[0021] The pharmaceutical compositions of the invention are typicallyformed by dissolving a therapeutic agent in ethanol to form atherapeutic agent solution. α-tocopherol is then added to thetherapeutic agent solution to form an α-tocopherol and therapeutic agentsolution. Next, the ethanol is removed to form a substantiallyethanol-free α-tocopherol and therapeutic agent solution. Thesubstantially ethanol free α-tocopherol and therapeutic agent solutionis blended with and without an aqueous phase incorporating a surfactantto form a pre-emulsion. For IV delivery the pre-emulsion is thenhomogenized to form a fine emulsion. For oral delivery, the pre-emulsionis typically encapsulated in a gelatin capsule.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The invention will be better understood by reference to thefigures, in which:

[0023]FIG. 1A shows the particle size of a paclitaxel emulsion (QWA) at7° C. over time;

[0024]FIG. 1B shows the particle size of a paclitaxel emulsion (QWA) at25° C. over time;

[0025]FIG. 2 is an HPLC chromatogram showing the integrity of apaclitaxel in an emulsion as described in Example 5;

[0026]FIG. 3A shows the paclitaxel concentration of a paclitaxelemulsion (QWA) at 4° C. over time;

[0027]FIG. 3B shows the paclitaxel concentration of a paclitaxelemulsion (QWA) at 25° C. over time; and

[0028]FIG. 4 shows the percentage of paclitaxel released over time fromthree different emulsions. The symbol • represents the percentage ofpaclitaxel released over time from an emulsion commercially availablefrom Bristol Myers Squibb. The symbol ▴ represents the percentage ofpaclitaxel released over time from an emulsion of this inventioncontaining 6 mg/ml paclitaxel (QWA) as described in Example 6. Thesymbol ⋄ represents the percentage of paclitaxel released over time froman emulsion of this invention (QWB) containing 7 mg/ml paclitaxel asdescribed in Example 7.

DETAILED DESCRIPTION OF THE INVENTION

[0029] To ensure a complete understanding of the invention the followingdefinitions are provided:

[0030] α-tocopherol: α-tocopherol, also known as vitamin E, is anorganic molecule with the following chemical structure (Scheme I):

[0031] In addition to its use as a primary solvent, α-tocopherol and itsderivatives are useful as a therapeutic agents.

[0032] Surfactants: Surface active group of amphiphilic molecules whichare manufactured by chemical processes or purified from natural sourcesor processes. These can be anionic, cationic, nonionic, andzwitterionic. Typical surfactants are described in Emulsions: Theory andPractice, Paul Becher, Robert E. Krieger Publishing, Malabar, Fla.,1965; Pharmaceutical Dosage Forms: Dispersed Systems Vol. I, Martin M.Rigear, Surfactants and U.S. Pat. No. 5,595,723 which is assigned to theassignee of this invention, Sonus Pharmaceuticals. All of thesereferences are hereby incorporated by reference.

[0033] TPGS: TPGS or PEGylated vitamin E is a vitamin E derivative inwhich polyethylene glycol subunits are attached by a succinic aciddiester at the ring hydroxyl of the vitamin E molecule. TPGS stands forD-α-tocopherol polyethyleneglycol 1000 succinate (MW=530). TPGS is anon-ionic surfactant (HLB=16-18) with the structure of Scheme II:

[0034] Various chemical derivatives of vitamin E TPGS including esterand ether linkages of various chemical moieties are included within thedefinition of vitamin E TPGS.

[0035] Polyethylene glycol: Polyethylene glycol (PEG) is a hydrophilic,polymerized form of ethylene glycol, consisting of repeating units ofthe chemical structure—(CH₂—CH₂—O—).

[0036] AUC: AUC is the area under the plasma concentration-time,commonly used in pharmacokinetics to quantitate the percentage of drugabsorption and elimination. A high AUC generally indicates that the drugwill successfully reach the target tissue or organ.

[0037] Poloxamers or Pluronics: are synthetic block copolymers ofethylene oxide and propylene oxide having the general structure:

OH(OCH₂CH₂)a(OCH₂CH₂CH₂)b(OCH₂CH₂)aH

[0038] The following variants based on the values of a and b arecommercially available from BASF Performance Chemicals (Parsippany,N.J.) under the trade name Pluronic and which consist of the group ofsurfactants designated by the CTFA name of Poloxamer 108, 188, 217, 237,238, 288, 338, 407, 101, 105, 122, 123, 124, 181, 182, 183, 184, 212,231, 282, 331, 401, 402, 185, 215, 234, 235, 284, 333, 334, 335, and403. For the most commonly used poloxamers 124, 188, 237, 338 and 407the values of a and b are 12/20, 79/28, 64/37, 141/44 and 101/56,respectively.

[0039] Solutol HS-15: is a polyethylene glycol 660 hydroxystearatemanufactured by BASF (Parsippany, N.J.). Apart from free polyethyleneglycol and its monoesters, di-esters are also detectable. According tothe manufacturer, a typical lot of Solutol HS-15 contains approximately30% free polyethylene glycol and 70% polyethylene glycol esters.

[0040] Other surfactants: Other surfactants useful in the inventioninclude ascorbyl-6 palmitate (Roche Vitamins, Nutley N.J.),stearylamine, and sucrose fatty acid esters (Mitsubishi Chemicals).Custom surfactants include those compounds with polar water-loving headsand hydrophobic tails, such as a vitamin E derivative comprising apeptide bonded polyglutamate attached to the ring hydroxyl and pegylatedphytosterol.

[0041] Hydrophile-lipophile balance: An empirical formula used to indexsurfactants. Its value varies from 1-45 and in the case of non-ionicsurfactants from about 1-20. In general for lipophilic surfactants theHLB is less than 10 and for hydrophilic ones the HLB is greater than 10.

[0042] Biocompatible: Capable of performing functions within or upon aliving organism in an acceptable manner, without undue toxicity orphysiological or pharmacological effects.

[0043] Substantially ethanol-free: A composition having an ethanolconcentration less than about 1.0% (w/v) ethanol.

[0044] Emulsion: A colloidal dispersion of two immiscible liquids in theform of droplets, whose diameter, in general, are between 0.1 and 3.0microns and which is typically optically opaque, unless the dispersedand continuous phases are refractive index matched. Such systems possessa finite stability, generally defined by the application or relevantreference system, which may be enhanced by the addition of amphiphilicmolecules or viscosity enhancers.

[0045] Microemulsion: A thermodynamically stable isotropically cleardispersion of two immiscible liquids, such as oil and water, stabilizedby an interfacial film of surfactant molecules. The microemulsion has amean droplet diameter of less than 200 nm, in general between 10-50 nm.In the absence of water, mixtures of oil(s) and non-ionic surfactant(s)form clear and isotropic solutions that are known as self-emulsifyingdrug delivery systems (SEDDS) and have successfully been used to improvelipophilic drug dissolution and oral absorption

[0046] Aqueous Medium: A water-containing liquid which can containpharmaceutically acceptable additives such as acidifying, alkalizing,buffering, chelating, complexing and solubilizing agents, antioxidantsand antimicrobial preservatives, humectants, suspending and/or viscositymodifying agents, tonicity and wetting or other biocompatible materials.

[0047] Therapeutic Agent: Any compound natural of synthetic which has abiological activity, is soluble in the oil phase and has anoctanol-buffer partition coefficient (Log P) of at least 2 to ensurethat the therapeutic agent is preferentially dissolved in the oil phaserather than the aqueous phase. This includes peptides, non-peptides andnucleotides. Lipid conjugates/prodrugs of water soluble molecules arewithin the scope of therapeutic agent.

[0048] Chemotherapeutic: Any natural or synthetic molecule which iseffective against one or more forms of cancer, and particularly thosemolecules which are slightly or completely lipophilic or which can bemodified to be lipophilic. This definition includes molecules which bytheir mechanism of action are cytotoxic (anti-cancer agents), thosewhich stimulate the immune system (immune stimulators) and modulators ofangiogenesis. The outcome in either case is the slowing of the growth ofcancer cells.

[0049] Chemotherapeutics include Taxol (paclitaxel) and relatedmolecules collectively termed taxoids, taxines or taxanes. The structureof paclitaxel is shown in the figure below (Scheme III).

[0050] Included within the definition of “taxoids” are variousmodifications and attachments to the basic ring structure (taxoidnucleus) as may be shown to be efficacious for reducing cancer cellgrowth and to partition into the oil (lipid phase) and which can beconstructed by organic chemical techniques known to those skilled in theart. The structure of the taxoid nucleus is shown in Scheme IV.

[0051] Chemotherapeutics include podophyllotoxins and their derivativesand analogues. The core ring structure of these molecules is shown inthe following figure (Scheme V):

[0052] Another important class of chemotherapeutics useful in thisinvention are camptothecins, the basic ring structure of which is shownin the following figure, but includes any derivatives and modificationsto this basic structure which retain efficacy and preserve thelipophilic character of the molecule shown below (Scheme VI).

[0053] Another preferred class of chemotherapeutics useful in thisinvention are the lipophilic anthracyclines, the basic ring structure ofwhich is shown in the following figure (Scheme VII):

[0054] Suitable lipophilic modifications of Scheme VII includesubstitutions at the ring hydroxyl group or sugar amino group.

[0055] Another important class of chemotherapeutics are compounds whichare lipophilic or can be made lipophilic by molecular chemosyntheticmodifications well known to those skilled in the art, for example bycombinatorial chemistry and by molecular modelling, and are drawn fromthe following list: Taxotere, Amonafide Illudin S,6-hydroxymethylacylfulvene Bryostatin 1, 26-succinylbryostatin 1,Palmitoyl Rhizoxin, DUP 941, Mitomycin B, Mitomycin C, Penclomedine.Interferon α2b, angiogenesis inhibitor compounds, Cisplatin hydrophobiccomplexes such as 2-hydrazino-4,5-dihydro-1H-imidazole with platinumchloride and 5-hydrazino-3,4-dihydro-2H-pyrrole with platinum chloride,vitamin A, vitamin E and its derivatives, particularly tocopherolsuccinate.

[0056] Other compounds useful in the invention include:1,3-bis(2-chloroethyl)-1-nitrosurea (“carmustine” or “BCNU”),5-fluorouracil, doxorubicin (“adriamycin”), epirubicin, aclarubicin,Bisantrene(bis(2-imidazolen-2-ylhydrazone)-9,10-anthracenedicarboxaldehyde,mitoxantrone, methotrexate, edatrexate, muramyl tripeptide, muramyldipeptide, lipopolysaccharides, 9-b-d-arabinofuranosyladenine(“vidarabine”) and its 2-fluoro derivative, resveratrol, retinoic acidand retinol, Carotenoids, and tamoxifen.

[0057] Other compounds useful in the application of this inventioninclude: Palmitoyl Rhizoxin, DUP 941, Mitomycin B, Mitomycin C,Penclomedine, Interferon α2b, Decarbazine, Lonidamine, Piroxantrone,Anthrapyrazoles, Etoposide, Camptothecin, 9-aminocamptothecin,9-nitrocamptothecin, camptothecin-11 (“Irinotecan’), Topotecan,Bleomycin, the Vinca alkaloids and their analogs [Vincristine,Vinorelbine, Vindesine, Vintripol, Vinxaltine, Ancitabine],6-aminochrysene, and navelbine.

[0058] Other compounds useful in the application of the invention aremimetics of taxol, eleutherobins, sarcodictyins, discodermolides andepothiolones.

[0059] Taking into account these definitions, the present invention isdirected to pharmaceutical compositions in the form of emulsions,micellar solutions or self-emulsifying drug delivery systems which aresubstantially free of ethanol solvent.

[0060] The therapeutic agents of the compositions of this invention caninitially be solublized in ethanol. However, the ethanol is removed inorder to form a substantially ethanol-free composition. The ethanolconcentration is less than 1% (w/v), preferably less than 0.5%, and mostpreferably less than 0.3%. The therapeutic agents can also besolubilized in methanol, propanol, chloroform, isopropanol, butanol andpentanol. These solvents are also removed prior to use.

[0061] The compositions of the invention contain α-tocopherol as acarrier for therapeutic drugs, which can be administered to animals orhumans via intravascular, oral, intramuscular, cutaneous andsubcutaneous routes. Specifically, the emulsions can be given by any ofthe following routes, among others: intraabdominal, intraarterial,intraarticular, intracapsular, intracervical, intracranial, intraductal,intradural, intralesional, intralocular, intralumbar, intramural,intraocular, intraoperative, intraparietal, intraperitoneal,intrapleural, intrapulmonary, intraspinal, intrathoracic, intratracheal,intratympanic, intrauterine, and intraventricular. The emulsions of thepresent invention can be nebulized using suitable aerosol propellantswhich are known in the art for pulmonary delivery of lipophiliccompounds.

[0062] In its first aspect, the invention is directed to the use ofα-tocopherol as the hydrophobic dispersed phase of emulsions containingwater insoluble, poorly water soluble therapeutic agents, water solubletherapeutic agents which have been modified to be less water soluble ormixtures thereof. Also called vitamin E, α-tocopherol is not a typicallipid oil. It has a higher polarity than most lipid oils, particularlytriglycerides, and is not saponifiable. It has practically no solubilityin water.

[0063] In the second aspect, the invention is a an α-tocopherol emulsionin the form of a self-emulsifying system where the system is to be usedfor the oral administration of water insoluble (or poorly water solubleor water soluble agents modified to be less water soluble or mixturesthereof) drugs where that is desired. In this embodiment, an oil phasewith surfactant and drug or drug mixture is encapsulated into a soft orhard gelatin capsule. Suitable solidification agents with melting pointsin the range of 40 to 60° C. such as high molecular weight polyethyleneglycols (MW>1000) and glycerides such as those available under the tradename Gellucires (Gattefose Corp. Saint Priest, France) can be added toallow filling of the formulation into a hard gelatin capsule at hightemperature. Semi-solid formulations are formed upon room temperatureequilbration. Upon dissolution of the gelatin in the stomach andduodenum, the oil is released and forms a fine emulsion with a meandroplet diameter of between 2-5 microns spontaneously. The emulsion isthen taken up by the microvilli of the intestine and released into thebloodstream.

[0064] In a third aspect, the invention comprises microemulsionscontaining α-tocopherol. Microemulsions refer to a sub-class ofemulsions where the emulsion suspension is essentially clear andindefinitely stable by virtue of the extremely small size of theoil/drug microaggregates dispersed therein.

[0065] In a fourth aspect of the invention, PEGylated vitamin E (TPGS)is used as a primary surfactant in emulsions of vitamin E. PEGylatedvitamin E is utilized as a primary surfactant, a stabilizer and also asa supplementary solvent in emulsions of vitamin E. Polyethylene glycol(PEG) is also useful as a secondary solvent in the emulsions of thisinvention.

[0066] The α-tocopherol concentration of the emulsions of this inventioncan be from about 2 to about 10% w/v. The ratio of α-tocopherol to TPGSis optimally from about 1:1 to about 10:1 (w/w).

[0067] The emulsions of the invention may further include surfactantssuch as ascorbyl-6 palmitate; stearylamine; sucrose fatty acid estersand various vitamin E derivatives comprising α-tocopherol nicotinate,tocopherol phosphate, and nonionic, synthetic surfactant mixtures,containing a fluorine-containing surfactant, such as the Zonyl brandseries and a polyoxypropylene-polyoxyethylene glycol nonionic blockcopolymer.

[0068] The emulsions of the invention can comprise an aqueous medium.The aqueous phase has an osmolality of approximately 300 mOsm and mayinclude potassium or sodium chloride sorbitol, mannitol, polyethyleneglycol, propylene glycol albumin, polypep and mixtures thereof. Thismedium can also contain various additives to assist in stabilizing theemulsion or in rendering the formulation biocompatible. Acceptableadditives include acidifying agents, alkalizing agents, antimicrobialpreservatives, antioxidants, buffering agents, chelating agents,suspending and/or viscosity-increasing agents, and tonicity agents.Preferably, agents to control the pH, tonicity, and increase viscosityare included. Optimally, a tonicity of at least 250 mOsm is achievedwith an agent which also increases viscosity, such as sorbitol orsucrose.

[0069] The emulsions of the invention for intravenous injection have aparticle size of 10 to 500 nm, preferably 10 to 200 nm and mostpreferably 10 to 100 nm. For intravenous emulsions, the spleen and liverwill eliminate particles greater than 500 mn in size through the RES.

[0070] A preferred form of the invention includes paclitaxel, a verywater-insoluble cytotoxin used in the treatment of uterine cancer andother carcinomas. An emulsion composition of the present inventioncomprises a solution of vitamin E containing paclitaxel at aconcentration of up to 20 mg/mL, four times that currently available byprescription, and a biocompatible surfactant such that the emulsionmicrodroplets are less than 0.2 microns and are terminally sterilizableby filtration.

[0071] A further embodiment of the invention is a method of treatingcarcinomas comprising the parenteral administration of a bolus dose ofpaclitaxel in vitamin E emulsion with and without PEGylated vitamin E byintravenous injection once daily or every second day over a therapeuticcourse of several weeks. Such method can be used for the treatment ofcarcinomas of the breast, lung, skin and uterus.

[0072] The general principles of the present invention may be more fullyappreciated by reference to the following non-limiting examples.

EXAMPLES Example 1

[0073] Dissolution of Paclitaxel in α-Tocopherol

[0074] α-Tocopherol was obtained from Sigma Chemical Company (St LouisMo.) in the form of a synthetic dl-α-tocopherol of 95% purity preparedfrom phytol. The oil was amber in color and very viscous. Paclitaxel waspurchased from Hauser Chemical Research (Boulder Colo.), and was 99.9%purity by HPLC. Paclitaxel 200 mg. was dissolved in 6 mL of dry absoluteethanol (Spectrum Chemical Manufacturing Corp, Gardenia Calif.) andadded to 1 gm α-tocopherol. The ethanol was then removed by vacuum at42° C. until the residue was brought to constant weight. Independentstudies showed that the ethanol content was less than 0.3% (w/v).

[0075] The resultant solution was clear, amber and very viscous, with anominal concentration of 200 mg/gm (w/w) paclitaxel in α-tocopherol.Higher concentrations of Paclitaxel (up to 400 mg/gm, w/w) can besolubilized in α-tocopherol.

Example 2

[0076] Anionic Surfactant Used to Prepare α-Tocopherol Emulsions

[0077] Paclitaxel 2 gm in 10 gm of α-tocopherol, prepared as describedin Example 1, was emulsified with ascorbyl palmitate as thetriethanolamine salt by the following method. A solution consisting ofascorbic acid 20 mM was buffered to pH 6.8 with triethanolamine as thefree base to from 2×buffer. 50 mL of the 2×buffer was placed in a Waringblender. 0.5 gm of ascorbyl-6-palmitate (Roche Vitamins and FineChemicals, Nutley N.J.), an anionic surfactant, was added and thesolution blended at high speed for 2 min at 40° C. under argon. Theα-tocopherol containing paclitaxel was then added into the blender withthe surfactant and buffer. Mixing was continued under argon until acoarse, milky, pre-emulsion was obtained, approximately after 1 min at40° C. Water for injection was then added, bringing the final volume to100 mL.

[0078] The pre-emulsion was transferred to the feed vessel of aMicrofluidizer Model 110Y (Microfluidics Inc, Newton Mass.). The unitwas immersed in a bath to maintain a process temperature ofapproximately 60° C. during homogenization, and was flushed with argonbefore use. After priming, the emulsion was passed through thehomogenizer in continuous re-cycle for 10 minutes at a pressure gradientof about 18 kpsi across the interaction head. The flow rate was about300 mL/min, indicating that about 25 passes through the homogenizerresulted.

[0079] The resultant paclitaxel emulsion in an α-tocopherol vehicle wasbottled in amber vials under argon and stored with refrigeration at 7°C. and 25° C. Samples were taken at discrete time intervals for particlesizing and chemical analysis.

[0080] Data taken with a Nicomp Model 370 Submicron Particle Sizer(Particle Sizing Systems Inc, Santa Barbara Calif.) showed that theemulsion had a mean particle diameter of 280 nm.

Example 3

[0081] Use of PEGylated Vitamin E (TPGS)

[0082] A ternary phase diagram was constructed for α-tocopherol,PEGylated vitamin E (TPGS, vitamin-Epolyoxyethyleneglycol-1000-succinate, obtained from Eastman ChemicalCo., Kingsport Tenn.), and water. TPGS was first melted at 42° C. andmixed gravimetrically with α-tocopherol at various proportions from 1 to100% TPGS, the balance being α-tocopherol. Mixtures were miscible at allconcentrations. Water was then added to each mixture in such a way thatthe final water concentration was increased stepwise from zero to 97.5%.At each step, observations were made of the phase behavior of themixture. As appropriate, mixing was performed by vortexing andsonication, and the mixture was heated or centrifuged to assess itsphase composition.

[0083] A broad area of biphasic o/w emulsions suitable for parenteraladministration was found at water concentrations above 80%. Theemulsions formed were milky white, free flowing liquids that containeddisperse α-tocopherol microparticles stabilized by non-ionic surfactant.Also in this area, microemulsions potentially suitable as drug carrierswere observed at TPGS to oil ratios above about 1:1. At lower watercontent, a broad area containing transparent gels (reverse emulsions)was noted. Separating the two areas (high and low water content) is anarea composed of opaque, soap-like liquid crystals.

[0084] Phase diagrams of α-tocopherol with surfactant combinations, forexample TPGS with a nonionic, anionic or cationic co-surfactant (forexample glutamyl stearate, ascorbyl palmitate or Pluronic F-68), or drugcan be prepared in a similar manner.

Example 4

[0085] α-Tocopherol Emulsion for Intravenous Delivery of Paclitaxel

[0086] A formulation of the following composition was prepared:Paclitaxel 1.0 gm % α-tocopherol 3.0 gm % TPGS 2.0 gm %Ascorbyl-6-Palmitate 0.25 gm % Sorbitol 5.0 gm % Triethanolamine to pH6.8 Water qs to 100 mL

[0087] The method of preparation was as follows: synthetic α-tocopherol(Roche Vitamins, Nutley N.J.), paclitaxel (Hauser, Boulder Colo.),ascorbyl 6-palmitate (Aldrich Chemical Co, Milwaukee Wis.) and TPGS weredissolved in 10 volumes of anhydrous undenatured, ethanol (SpectrumQuality Products, Gardenia Calif.) with heating to 40-45° C. The ethanolwas then drawn off with vacuum until no more than 0.3% remained byweight.

[0088] Pre-warmed aqueous solution containing a biocompatible osmolyteand buffer were added with gentle mixing and a white milk formedimmediately. This mixture was further improved by gentle rotation for 10minutes with continuous warming at 40-45° C. This pre-mixture at aboutpH 7 was then further emulsified as described below.

[0089] The pre-mixture at 40-45° C. was homogenized in an Avestin C5homogenizer (Avestin, Ottawa Canada) at 26 Kpsi for 12 minutes at 44° C.The resultant mixture contained microparticles of α-tocopherol with amean size of about 200 nm. Further pH adjustment was made with analkaline 1 M solution of triethanolamine (Spectrum Quality Products).

[0090] In order to avoid gelation of the TPGS during the early stage ofemulsification, all operations were performed above 40° C. and care wastaken to avoid exposure of the solutions to cold air by covering allvessels containing the mixture. Secondly, less than 2% TPGS shouldgenerally be dissolved in α-tocopherol oil before pre-emulsification,the balance of the TPGS being first dissolved in the aqueous bufferbefore the pre-emulsion is prepared. The solution gels at concentrationsof TPGS higher than 2%.

[0091] Physical stability of the emulsion was then examined by placingmultiple vials on storage at 4° C. and 25° C. Over several months, vialswere periodically withdrawn for particle sizing. Mean particle size, asdetermined with the Nicomp Model 370 (Particle Sizing Systems, SantaBarbara Calif.), is shown for the two storage temperatures in FIG. 1.The particle size distribution was bi-modal.

Example 5

[0092] Chemical Stability of Paclitaxel in an α-Tocopherol Emulsion

[0093] After emulsification, the formulation of Example 4 was analyzedfor paclitaxel on a Phenosphere CN column (5 microns, 150×4.6 mm). Themobile phase consisted of a methanol/water gradient, with a flow rate of1.0 mL/min. A UV detector set at 230 nm was used to detect andquantitate paclitaxel. A single peak was detected (FIG. 2), which had aretention time and mass spectrogram consistent with native referencepaclitaxel obtained from Hauser Chemical (Boulder Colo.).

[0094] Chemical stability of the emulsion of example 4 was examined byHPLC during storage. The data of FIG. 3 demonstrate that paclitaxelremains stable in the emulsion for periods of at least 3 months,independent of the storage temperature. Taken together, the data ofFIGS. 2 and 3 demonstrate successful retention of drug potency andemulsion stability when stored at 4° C. for a period of at least 3months.

Example 6

[0095] Paclitaxel Emulsion Formulation QWA

[0096] An emulsion of paclitaxel 10 mg/ml for intravenous drug delivery,having the following composition, was prepared as described in Example4. Paclitaxel 1.0 gm % α-tocopherol 3.0 gm % TPGS 1.5 gm %Ascorbyl-6-Palmitate 0.25 gm % Sorbitol 4.0 gm % Triethanolamine to pH6.8 Water qs to 100 mL

Example 7

[0097] Paclitaxel Emulsion Formulation QWB

[0098] A second emulsion of paclitaxel 10 mg/ml for intravenous drugdelivery, having the following composition, was prepared as described inExample 4. Paclitaxel 1.0 gm % α-tocopherol 3.0 gm % TPGS 1.5 gm %Solutol HS-15 1.0 gm % Sorbitol 4.0 gm % Triethanolamine to pH 6.8 Waterqs to 100 mL

[0099] Solutol HS-15 is a product of BASF Corp, Mount Olive N.J.

Example 8

[0100] 10 mg/mL Paclitaxel Emulsion Formulation QWC

[0101] A third emulsion formulation of paclitaxel 10 mg/ml was preparedas follows using Poloxamer 407 (BASF Corp, Parsippany N.J.) as aco-surfactant. Paclitaxel 1.0 gm % α-tocopherol 6.0 gm % TPGS 3.0 gm %Poloxamer 407 1.0 gm % Sorbitol 4.0 gm % Triethanolamine to pH 6.8 Waterfor injection qs to 100 mL

[0102] In this example, 1.0 gm Poloxamer 407 and 1.0 gm paclitaxel weredissolved in 6.0 gm α-tocopherol with ethanol 10 volumes and gentleheating. The ethanol was then removed under vacuum. Separately, anaqueous buffer was prepared by dissolving 3.0 gm TPGS and 4.0 gmsorbitol in a final volume of 90 mL water for injection. Both oil andwater solutions were warmed to 45° C. and mixed with sonication to makea pre-emulsion. A vacuum was used to remove excess air from thepre-emulsion before homogenization.

[0103] Homogenization was performed in an Avestin C5 as alreadydescribed. The pressure differential across the homogenization valve was25 kpsi and the temperature of the feed was 42-45° C. A chiller was usedto ensure that the product exiting the homogenizer did not exceed atemperature of 50° C. Flow rates of 50 mL/min were obtained duringhomogenization. After about 20 passes in a recycling mode, the emulsionbecame more translucent. Homogenization was continued for 20 min.Samples were collected and sealed in vials as described before. A fineα-tocopherol emulsion for intravenous delivery of paclitaxel wasobtained. The mean particle diameter of the emulsion was 77 nm.Following 0.22μ sterile filtration through a 0.22 micron Durapore filter(Millipore Corp, Bedford Mass.), the emulsion was filled in vials andstored at 4° C. until used for intravenous injection.

Example 9

[0104] 5 mg/mL Paclitaxel Emulsion Formulation QWC

[0105] An additional emulsion of paclitaxel was prepared as described inExample 8 but incorporating 5 instead of 10 mg/ml of the drug. Thecomposition of this emulsion is as follows: Paclitaxel 0.5 gm %α-tocopherol 6.0 gm % TPGS 3.0 gm % Poloxamer 407 1.0 gm % Sorbitol 4.0gm % Triethanolamine to pH 6.8 Water for injection qs to 100 mL

[0106] Following homogenization as described in example 8, a somewhattranslucent emulsion of α-tocopherol and paclitaxel with a mean particlediameter of 52 nm was obtained. Following sterile filtration through a0.22 micron Durapore filter (Millipore Corp, Bedford Mass.), theemulsion was filled in vials and stored at 4° C. until used forintravenous injection. Drug losses on filtration were less than 1%.

Example 10

[0107] Paclitaxel Emulsion Formulation QWD

[0108] A fifth emulsion of α-tocopherol for intravenous administrationof paclitaxel was prepared as follows: Paclitaxel 0.5 gm % α-tocopherol6.0 gm % TPGS 3.0 gm % Poloxamer 407 1.5 gm % Polyethyleneglycol 200 0.7gm % Sorbitol 4.0 gm % Triethanolamine to pH 6.8 Water for injection qsto 100 mL

[0109] Synthetic α-tocopherol USP-FCC obtained from Roche Vitamins(Nutley, N.J.) was used in this formation. Polyethyleneglycol 200(PEG-200) was obtained from Sigma Chemical Co.

[0110] Following homogenization, a somewhat translucent emulsion with amean particle diameter of 60 nm was obtained. Following 0.22μ sterilefiltration through a 0.22 micron Durapore filter (Millipore Corp,Bedford Mass.), the emulsion was filled in vials and stored at 4° C.until used for intravenous injection. Drug losses on filtration wereless than 1%.

Example 11

[0111] Dissolution of Paclitaxel in TPGS and Preparation of MicellarSolutions

[0112] We observed good solubility of paclitaxel in TPGS, about 100 mgdrug per 1.0 gm of TPGS. Micellar solutions of TPGS containingpaclitaxel were prepared as follows. A stock solution of paclitaxel inTPGS was made up by dissolving 90 mg paclitaxel in 1.0 gm TPGS at 45° C.with ethanol, which was then removed under vacuum. Serial dilutions werethen prepared by diluting the paclitaxel stock with additional TPGS toobtain paclitaxel in TPGS at concentrations of 0.1, 1, 5, 10, 25, 50, 75and 90 mg/mL. Using fresh test tubes, 100 mg of each paclitaxelconcentration in TPGS was dissolved in 0.9 mL water. All test tubes weremixed by vortex and by sonication at 45° C. Clear micellar solutions inwater were obtained corresponding to final paclitaxel concentrations of0.01, 0.1, 0.5, 1.0, 2.5, 5.0, 7.5 and 9.0 mg/mL.

[0113] A Nicomp Model 370 laser particle sizer (Particle Sizing Systems,Santa Barbara Calif.) was used to examine the solutions. Particle sizeson the order of 10 nm were obtained, consistent with the presence ofmicelles of TPGS and paclitaxel.

[0114] Micellar solutions of paclitaxel in TPGS containing up to 2.5mg/mL paclitaxel were stable for at least 24 hr whereas those at 5.0,7.5 and 9.0 mg/mL were unstable and drug crystals formed rapidly andirreversibly. These observations imply that paclitaxel remainssolubilized only in the presence of an α-tocopherol-rich domain withinthe emulsion particles. Thus, an optimum ratio of α-tocopherol to TPGSis needed in order to produce emulsions in which higher concentrationsof paclitaxel can be stabilized.

[0115] When adjusted to the proper tonicity and pH, micellar solutionshave utility for slow IV drip administration of paclitaxel to cancerpatients, although the AUC is expected to be low.

[0116] The utility of TPGS in α-tocopherol emulsions is a synergy ofseveral desirable characteristics. First, it has its own affinity forpaclitaxel, probably by virtue of the α-tocopherol that makes up thehydrophobic portion of its molecular structure. Secondly, interfacialtension of TPGS in water with α-tocopherol is about 10 dynes/cm,sufficient to emulsify free α-tocopherol, especially when used with aco-surfactant. Third, polyoxyethylated surfactants such as TPGS, havewell established, superior properties as a “stealth coat” for injectableparticles, by dramatically reducing trapping of the particles in theliver and spleen, as is well known in the art. But the unexpected andunique finding with TPGS as a surfactant for α-tocopherol emulsions, wasthe finding of all three desirable characteristics in a single molecule.An additional advantage of TPGS is the fact that it forms stableself-emulsifying systems in mixtures with oils and solvents such aspropylene glycol and polyethylene glycol, suggesting a synergy when usedwith α-tocopherol for oral drug delivery.

[0117] When adjusted to the proper tonicity and pH, micellar solutionshave utility for slow IV drip administration of paclitaxel to cancerpatients, although the AUC is expected to be low.

Example 12

[0118] 20 mg/mL Paclitaxel Emulsion Formulation

[0119] A coarse, emulsion containing 20 mg/mL paclitaxel in α-tocopherolwas obtained with 5% α-tocopherol and 5% TPGS by the methods describedin Example 4, simply by increasing the concentrations. No effort wasmade to test higher concentrations simply because no further increase isnecessary for clinically useful intravenous emulsions.

Example 13

[0120] Use of other PEG Surfactants in α-Tocopherol Emulsions

[0121] A variety of other pegylated surfactants, for example TritonX-100, PEG 25 propylene glycol stearate, Brij 35 (Sigma Chemical Co),Myrj 45, 52 and 100, Tween 80 (Spectrum Quality Products), PEG 25glyceryl trioleate (Goldschmidt Chemical Corp, Hopewell Va.), haveutility in emulsifying α-tocopherol.

[0122] However, experiments with other pegylated surfactants failed toconvincingly stabilize paclitaxel in an α-tocopherol emulsion. Todemonstrate the unique utility of TPGS, three emulsions were prepared asdescribed in Example 9, but Tween 80 and Myrj 52 were substituted forTPGS as the primary surfactant in separate emulsions. These twosurfactants were chosen because Tween 80 and Myrj 52 have HLB valuesessentially equivalent to TPGS and make reasonably good emulsions ofα-tocopherol. However, when 5 mg/mL paclitaxel was included in theformulation, drug crystallization was noted very rapidly afterpreparation of the pre-emulsion, and the processed emulsions of Tween 80and Myrj 52 were characterized as coarse, containing rod-shapedparticles up to several microns in length, consistent with crystals ofpaclitaxel. Unlike the TPGS emulsion, which passed readily through a0.22 micron filter with less than 1% loss of drug, the Tween and Myrjemulsions were unfilterable because of the presence of this crystallinedrug material.

[0123] There are several possible explanations for the unexpectedimprovement of the α-tocopherol paclitaxel emulsions with TPGS. The drughas good solubility in TPGS, up to about 100 mg/mL. Most likely it isthe strength of the affinity of paclitaxel benzyl side chains with theplanar structure of the α-tocopherol phenolic ring in the TPGS moleculethat stabilizes the complex of drug and carrier. In addition thesuccinate linker between the α-tocopherol and PEG tail is a novelfeature of this molecule that distinguishes its structure from otherPEGylated surfactants tested.

Example 14

[0124] Poloxamer-based α-Tocopherol Emulsion α-tocopherol 6.0 gm %Poloxamer 407 2.5 gm % Ascorbyl Palmitate 0.3 gm % Sorbitol 6.0 gm %Triethanolamine to pH 7.4 Water qs to 100 mL

[0125] An α-tocopherol emulsion was prepared using Poloxamer 407 (BASF)as the primary surfactant. The white milky pre-mixture was homogenizedwith continuous recycling for 10 minutes at 25 Kpsi in a C5 homogenizer(Avestin, Ottawa Canada) with a feed temperature of 45° C. and a chillerloop for the product out set at 15° C. A fine, sterile filterableemulsion of α-tocopherol microparticles resulted. However, when thisformulation was made with paclitaxel, precipitation of the paclitaxelwas noted following overnight storage in the refringerator, againunderlying the superior utility of TPGS as the principle surfactant.

Example 15

[0126] Lyophilized Emulsion Formulation

[0127] Maltrin M100 (Grain Processing Corporation, Muscatine Iowa) wasadded as a 2×stock in water to the emulsion of Example 14. Aliquots werethen frozen in a shell freezer and lyophilized under vacuum. Onreconstitution with water, a fine emulsion was recovered.

[0128] Lyophilized formulations have utility where the indefinite shelflife of a lyophilized preparation is preferred. Lyophilizableformulations containing other saccharides, such as mannitol, albumin orPolyPep from Sigma Chemicals, St. Louis, Mo. can also be prepared.

Example 16

[0129] In vitro Release of Paclitaxel from α-Tocopherol Emulsions

[0130] One of the desired characteristics of a drug delivery vehicle isto provide sustained release of the incorporated drug, a characteristicquite often correlated with improved pharmacokinetics and efficacy. Inparticular, long-circulating emulsions of paclitaxel can improve thedelivery of the drug to cancer sites in the body. We have surprisinglyfound that the emulsions of the present invention do provide sustainedrelease of paclitaxel when compared to the only FDA-approved formulationof paclitaxel at this time [Taxol®, Bristol Myers Squibb(BMS), PrincetonN.J.]. Emulsions were prepared having paclitaxel concentrations of 6mg/mL (QWA) and 7 mg/mL (QWB). For comparison, Taxol contains 6 mg/ml ofpaclitaxel dissolved in ethanol:cremophore EL 1:1 (v/v). In vitrorelease of paclitaxel from the different formulations into a solution ofphosphate-buffered saline (PBS) at 37° C. was monitored using a dialysismembrane that is freely permeable to paclitaxel (MW cut-off of 10kilodaltons). Quantification of the drug in pre- and post-dialysissamples was performed by HPLC. Drug release profiles in terms of bothpercent release and concentration of paclitaxel released over time weregenerated. As can be seen from the data in FIG. 4, less than 5% ofpaclitaxel was dialyzed from the emulsions over 24 hr, whereas about 12%was recovered outside the dialysis bag from the marketed BMSformulation. This indicates that drug release from the emulsion wassignificantly slowed relative to the commercially available solution.

Example 17

[0131] Biocompatibility of α-Tocopherol Emulsions Containing Paclitaxel

[0132] An acute single-dose toxicity study was performed. Mice 20-25 gmeach were purchased and acclimatized in an approved animal facility.Groups of mice (n=3) received doses of the formulation containing from30 to 90 mg/kg paclitaxel in the α-tocopherol emulsion prepared asdescribed in Example 6. All injections were given intravenously bytailvein bolus.

[0133] Although all injections were given by bolus IV push, no deaths orimmediate toxicity were observed at any dose, even at 90 mg/kg. Theresults for body weight are shown in Table 1. Weight loss was 17% in thehighest group but all groups, even at 90 mg/kg, recovered or gained bodyweight over a period of 10 days post injection.

[0134] A vehicle toxicity study was also done. Animals receivingdrug-free emulsion grew rapidly, and gained slightly more weight thananimals receiving saline or not injected. This was attributed to thevitamin and calorie content of the formulation.

[0135] We observed a maximal tolerable dose (MTD) for paclitaxel ofgreater than 90 mg/kg (Table 1), with no adverse reactions noted. Thisis more than double the best literature values reported, in which deathswere observed at much smaller doses. Taxol, the FDA-approved BMSformulation, causes death in mice at bolus intravenous doses of 10mg/kg, a finding repeated in our hands. In the rat, BMS Taxol wasuniformly fatal at all dilutions and dose regimes we tested. Incontrast, the composition of Example 6 was well tolerated in rats, andis even improved over Taxotere, a less toxic paclitaxel analoguecommercially marketed by Rhone-Poulenc Rorer.

[0136] One possible explanation for the high drug tolerance is that theemulsion is behaving as a slow-release depot for the drug as suggestedfrom the in vitro release data in Example 16. TABLE 1 Average BodyWeight Change of Mice Treated with Paclitaxel Emulsion Treatment Numberof BW Change (gm) (dose, mg/kg) Animals Day 2 Day 7 Saline 4 1.0 3.4Vehicle 4 1.2 3.5 Paclitaxel Emulsion 2 −1.0 2.2 (QWA) (36.3) PaclitaxelEmulsion 4 −1.8 1.7 (QWA) (54.4) Paclitaxel Emulsion 4 −1.5 1.6 (QWA)(72.6) Paclitaxel Emulsion 1 −1.6 (QWA) (90.7)

Example 18

[0137] Efficacy Evaluation of Paclitaxel Emulsion

[0138] The paclitaxel emulsion of Example 6 was also evaluated forefficacy against staged B16 melanoma tumors in nude mice and the data isshown in Table 2. Once again, the marketed product BMS Taxol was used asa reference formulation. Tumor cells were administered subcutaneouslyand therapy started by a tail vein injection at day 4 post-tumoradministration at the indicated dosing schedule. Efficacy was expressedas percent increase in life-span (% ILS).

[0139] The following conclusions can be drawn from the data in Table 2:a) an increased life span of about 10% was obtained by administration ofBMS Taxol at 10 mg/kg Q2D×4, b) %ILS values improved to 30-50% byadministration of the α-tocopherol emulsion of paclitaxel at 30, 40 or50 mg/kg Q2D×4, dose levels made possible by the higher MTD, c) a nicedose response was observed when the emulsion was administered at 30, 50and 70 mg/kg Q4D×3, with about 80% ILS being observed at 70 mg/kg and,d) even at 90 mg/kg dosed only once at day 4, there was about 36% ILS.These data clearly illustrate the potential of the emulsions of thepresent invention to substantially improve the efficacy of paclitaxel.

Example 19

[0140] Efficacy Evaluation of Paclitaxel Emulsions

[0141] The emulsions of examples 6, 7 and 8 (QWA, QWB and QWCrespectively) were compared for efficacy against B16 melanoma in mice;BMS taxol was again used as a reference formulation. Methods essentiallyidentical to those of Example 18 were used. The data from this study issummarized in Table 3. Efficacy was expressed as: a) percent tumorgrowth inhibition (% T/C, where T and C stand for treated and controlanimals, respectively); b) tumor growth delay value (T-C), and c) logcell kill which is defined as the ratio of the T-C value over 3.32×tumordoubling time. The latter parameter for this particular tumor model wascalculated to be 1.75 days. As can be seen from the results in Table 3,all measures of efficacy: tumor growth inhibition, tumor growth delayvalue and log cell kill demonstrate superior efficacy of α-tocopherolemulsions as a drug delivery vehicle over BMS Taxol, particularly whenthe emulsions were dosed every four days at 70 mg/kg. As explained inExample 16, this increased efficacy is likely a result of improved drugbiocompatibility and/or sustained release. TABLE 2 Survival of Mice withB16 Tumors Treated with QWA and BMS Taxol Mean Survival % ILS^(b) Time,Days (vs vehicle) (Mean ± (Mean ± Treatment Group & Schedule S.E.M^(a))S.E.M) Vehicle Control (Days 4, 8, 12) 13.2 ± 0.9 — Saline Control (Days4, 8, 12) 15.8 ± 1.2 19.7 ± 8.6 BMS Taxol (10 mg/kg) 16.4 ± 0.7 24.2 ±5.4 (Days 4, 6, 8, 10) QWA (30 mg/kg) (Days 4, 6, 8) 19.2 ± 1.4 45.4 ±10.3 QWA (40 mg/kg) (Days 4, 6, 8) 21.3 ± 1.4 61.4 ± 10.3 QWA (50 mg/kg)(Days 4, 6, 8) 18.8 ± 0.7 42.4 ± 5.7 QWA (30 mg/kg) (Days 4, 8, 12) 15.3± 0.8 15.9 ± 6.4 QWA (50 mg/kg) (Days 4, 8, 12) 20.7 ± 1.3 56.8 ± 9.5QWA (70 mg/kg) (Days 4, 8, 12) 24.2 ± 0.9 83.3 ± 6.4 QWA (90 mg/kg) (Day4 only) 18.0 ± 0.6 36.4 ± 4.4

[0142] TABLE 3 Comparison of 3 paclitaxel emulsions and BMS taxolagainst early-stage B16 melanoma Total Median tumor Median tumor wt.Dosage Dosing Schedule Dose wt. on day 15 on day 18 mg % T/C T-C Logcell Test Article mg/kg/day (days) (mg/kg) (mg) (range) Day 15 (days)kill total Control  0 4, 6, 8, 10  0 836 2139  — — — BMS Taxol 20 4, 6,8, 10 80 383 1217  46 2 0.34 QWA 20 4, 6, 8, 10 80 381 1197  46 2 0.34QWA 40 4, 6, 8, 10 160  104 306 12 7 1.2  QWA 70 4, 8, 12, 16, 20 350  15  11 −2 QWB 20 4, 6, 8, 10 80 197 653 24 5 0.86 QWB 30 4, 6, 8, 10120  139 449 17 5 0.86 QWB 40 Toxic QWC 20 4, 6, 8, 10 80 319 848 34 30.52 QWC 40 4, 6, 8, 10 160   53 194  6 8 1.4  QWC 70 4, 8, 12, 16, 20350   33  66  4 >15  >2.6 

Example 20

[0143] Self-emulsification of an α-Tocopherol/Tagat TO Mixture

[0144] α-tocopherol 2.0 gm and Tagat TO (Goldschmidt Chemical Corp,Hopewell Va.) 800 mg were dissolved together. About 80 mg of the oilymixture was transferred to a test tube and water was then added. Withgentle hand mixing, there was immediate development of a rich milkyemulsion, consistent with “self-emulsifying systems” proposed as drugdelivery systems, in which surfactant-oil mixtures spontaneously form anemulsion upon exposure to aqueous media.

Example 21

[0145] Self-emulsifying Formulation Containing Paclitaxel

[0146] Paclitaxel 50 mg/ml was prepared in α-tocopherol by the methoddescribed in Example 1. Tagat TO 20% (w/w) was added. The resultantmixture was clear, viscous and amber in color. A 100 mg quantity of theoily mixture was transferred to a test tube. On addition of 1 mL ofwater, with vortex mixing, a fine emulsion resulted.

Example 22

[0147] Self-emulsifying Formulation of Paclitaxel

[0148] Paclitaxel 50 mg/ml was prepared in α-tocopherol by the methoddescribed in Example 1. After removal of the ethanol under vacuum, 20%TPGS and 10% polyoxyethyleneglycol 200 (Sigma Chemical Co) were added byweight. A demonstration of the self-emulsification ability of thissystem was then performed by adding 20 mL of deionized water to 100 mgof the oily mixture at 37° C. Upon gentle mixing, a white, thin emulsionformed, consisting of fine emulsion particles demonstrated with theMalvern Mastersizer (Malvern Instruments, Worcester Mass.) to have amean size of 2 microns, and a cumulative distribution 90% of which wasless than 10 microns.

Example 23

[0149] Etoposide Emulsion Formulation in α-Tocopherol

[0150] Etoposide 4 mg (Sigma Chemical Co) was dissolved in the followingsurfactant-oil mixture: Etoposide 4 mg α-tocopherol 300 mg TPGS 50 mgPoloxamer 407 50 mg

[0151] Ethanol and gentle warming was used to form a clear ambersolution of drug in oil. The ethanol was then removed under vacuum.

[0152] A pre-emulsion was formed by adding 4.5 mL of water containing 4%sorbitol and 100 mg TPGS at 45° C. with sonication. The particle sizewas further reduced by processing in an Emulsiflex 1000 (Avestin, OttawaCanada). The body of the Emulsiflex 1000 was fitted with a pair of 5 mLsyringes and the entire apparatus heated to 45° C. before use. The 5 mLof emulsion was then passed through it by hand approximately 10 times. Afree flowing, practical emulsion of etoposide in an α-tocopherol vehicleresulted.

[0153] We note that the solubilized form of etopside in α-tocopherol canalso be used as an oral dosage form by adaption of the methods of thepreceding examples.

Example 24

[0154] Dissolution of Ibuprofen or Griseofulvin in α-Tocopherol

[0155] Ibuprofen is a pain-killer, and may be administered by injectionwhen required if there is danger that the drug will irritate thestomach. The following solution of ibuprofen in α-tocopherol may beemulsified for intravenous administration.

[0156] Ibuprofen (Sigma Chemicals), 12 mg. crystalline, dissolvedwithout solvent in α-tocopherol, 120 mg, by gentle heating. Theresultant 10% solution of ibuprofen in vitamin E can be emulsified bythe method s described in Examples 4, 6, 7, 8 or 22.

[0157] An antifungal compound, griseofulvin, 12 mg, was first dissolvedin 3 mL of anhydrous ethanol; α-tocopherol was then added, 180 mg, andthe ethanol was removed with gentle heating under vacuum. The resultantsolution of griseofulvin in α-tocopherol is clear and can be emulsifiedby the methods described in Examples 4, 6, 7, 8 or 22.

Example 25

[0158] Vitamin E Succinate Emulsion Formulation

[0159] Vitamin E succinate has been suggested as a therapeutic for thetreatment of lymphomas and leukemias and for the chemoprevention ofcancer. The following is a composition and method for the emulsificationof vitamin E succinate in α-tocopherol. Sucrose ester S1170 is a productof Mitsubishi Kagaku Foods Corp, Tokyo Japan. Vitamin E succinate, asthe free acid, was obtained as a whitish powder from ICN Biomedicals,Aurora, Ohio. Emulsions incorporating other surfactants such aspluronics, and TPGS along with α-tocopherol and α-tocopherol succinatecan be prepared in a similar manner with and without a therapeuticagent.

[0160] α-Tocopherol 8 gm and vitamin E succinate 0.8 gm were dissolvedtogether in ethanol in a round bottom flask. After removal of thesolvent, 100 mL of an aqueous buffer was added. The alkaline bufferconsisting of 2% glycerol, 10 mM triethanolamine, and 0.5 gm % sucroseester S1170. After mixing for 2 min, the pre-emulsion was transferred toan Avestin Model C-5 homogenizer and homogenization was continued forabout 12 minutes at a process feed temperature of 58° C. The pressuredifferential across the interaction head was 25 to 26 kpsi. Duringhomogenization, pH was carefully monitored, and adjusted as required topH 7.0. Care was taken to exclude oxygen during the process. A finewhite emulsion resulted.

Example 26

[0161] α-Tocopherol Levels in Esters

[0162] Levels of α-tocopherol in commerically available esters:tocopherol-acetate, -succinate, -nicotinate, -phosphate and TPGS wereeither provided by the vendor or determined by HPLC. The concentrationof free α-tocopherol in these solutions is less than 1.0%, generallyless than 0.5%.

Example 27

[0163] Resveratrol Emulsion Formulation

[0164] Resveratrol is a cancer chemopreventative first discovered as anextract of grape skins. It has been proposed as a dietary supplement.

[0165] Resveratrol was obtained from Sigma Chemical Co. While itdissolved poorly in ethanol, upon addition of 10 mg resveratrol, 100 mgof α-tocopherol, 100 mg TPGS and ethanol, a clear solution formedrapidly. Upon removal of the ethanol, a clear amber oil remained.

[0166] The oily solution of resveratrol can be formulated as aself-emulsifying system for oral delivery by the various methods of thepreceding examples.

Example 28

[0167] Muramyl Dipeptide Formulation

[0168] Muramyl dipeptides are derived from mycobacteria and are potentimmunostimulants representative of the class of muramyl peptides,mycolic acid and lipopolysaccharides. They have use, for example, in thetreatment of cancer, by stimulating the immune system to target andremove the cancer. More recently, muroctasin, a synthetic analog, hasbeen proposed to reduce non-specific side effects of the bacterial wallextracts.

[0169] N-acetylmuramyl-6-O-steroyl-1-alanyl-d-isoglutamine was purchasedfrom Sigma Chemical Co. and 10 mg was dissolved in 100 mg α-tocopheroland 80 mg TPGS. Ethanol was used as a co-solvent to aid in dissolutionof the dipeptide, but was removed by evaporation under vacuum, leaving aclear solution in α-tocopherol and surfactant.

[0170] This oil solution of the drug can be emulsified for parenteraladministration by the various methods of the preceding examples.

Example 29

[0171] Alcohol-containing Emulsion

[0172] In attempting to adapt the teachings of PCT WO 95/11039 to theoral administration of paclitaxel, the following formulation was made.Paclitaxel 0.125 gm α-tocopherol 0.325 gm TPGS 0.425 gm Ethanol 0.125 gm

[0173] As before, paclitaxel was dissolved in a α-tocopherol and TPGSwith ethanol, which was then removed under vacuum. By dry weight,residual ethanol was less than 3 mg (0.3% w/w). Fresh anhydrous ethanol0.125 gm was then added back to the formulation. After mixing thesuitability of the formulation for oral administration, as in a gelatincapsule, was simulated by the following experiment. An aliquot of 100 mgof the free-flowing oil was added to 20 mL of water at 37° C. and mixedgently with a vortex mixer. A fine emulsion resulted. But after twentyminutes, microscopy revealed the growth on large numbers of crystals inrosettes, characteristic of paclitaxel precipitation. It was concludedthat this formulation was not suitable for oral administration ofpaclitaxel because large amounts of the drug would be in the form ofcrystals on entry into the duodenum, where it would be prevented fromuptake because of its physical form. We speculate that the excess ofethanol, in combination with the high ratio of TPGS to α-tocopherol, isresponsible for the observed crystallization of the drug from thisformulation.

Example 30

[0174] Alcohol-containing α-Tocopherol Emulsion

[0175] In attempting to adapt the teachings of PCT WO 95/11039 to theintravenous administration of paclitaxel, the following formulation wasmade: Paclitaxel 0.050 gm α-tocopherol 0.100 gm Lecithin 0.200 gmEthanol 0.100 gm Butanol 0.500 gm

[0176] As before, paclitaxel was dissolved in α-tocopherol and TPGS withethanol, which was then removed under vacuum. By dry weight, residualethanol was less than 2 mg (0.5% w/w). Fresh anhydrous ethanol 0.100 gmand n-butanol 0.500 gm was then added back to the formulation. A clearoil resulted. The injection concentrate was tested for biocompatibilityin administration by standard pharmaceutical practice of admixture andsaline. About 200 mg of the oil was dropped into 20 mL of saline andmixed. Large flakes of insoluble material developed immediately and thegreatest amount of material formed dense deposits on the walls of thetest tube. The mixture was clearly unsuitable for parenteraladministration by any route, and we speculate that this is so regardlessof the identity of the drug contained in the formulation. By trial anderror we have learned that lecithin is a poor choice as surfactant forα-tocopherol by virtue of its low HLB (around 4). Other successfulexamples described here for fine emulsions suitable for parenteraladministration were all made with high HLB surfactants. Thesesurfactants include TPGS (HLB around 17), Poloxamer 407 (HLB about 22)and Tagat TO (HLB about 14.0). In general, we found that α-tocopherolemulsification is best performed with principal surfactants of HLB>10,preferably greater than 12. Lecithin is not in this class, although itcould be used as a co-surfactant. In comparison, typical o/w emulsionsof triglycerides are made with surfactants of HLB between 7 and 12,demonstrating that α-tocopherol emulsions are a unique class by virtueof the polarity and extreme hydrophobicity of the α-tocopherol, factorsthat also favor the solubility of lipophilic and slightly polarlipophilic drugs in α-tocopherol. See Emulsions: Theory and Practice,2nd Ed. p.248 (1985).

We claim:
 1. A pharmaceutical composition, comprising: α-tocopherol, oneor more surfactants, an aqueous phase, and a therapeutic agent whereinsaid composition is in the form of an emulsion or micellar solution. 2.The composition of claim 1 wherein said surfactant is an α-tocopherolderivative.
 3. The composition of claim 2 wherein said vitamin Ederivative is an ester or an ether of α-tocopherol and polyethyleneglycol.
 4. The composition of claim 2 wherein said vitamin E derivativeis TPGS.
 5. The composition of claim 4 wherein the ratio of α-tocopherolto TPGS is from about 1:1 to about 10:1 w/w.
 6. The composition of claim5 further including a second surfactant wherein said second surfactanthas an HLB of at least
 10. 7. The composition of claim 6 wherein saidsecond surfactant is selected from the group consisting of anionic,cationic, nonionic and zwitterionic surfactants.
 8. The composition ofclaim 7 wherein said second surfactant is selected from the groupconsisting of poloxypropylene-polyoxyethylene glycol nonionic blockpoplymers, ascorbyl-6-palmitate, stearylamine and sucrose fatty esters.9. The composition of claim 8 wherein said second surfactant isascorbyl-6-palmitate.
 10. The composition of claim 8 wherein said secondsurfactant has a structure: OH(OCH₂CH₂)a(OCH₂CH₂CH₂)b(OCH₂CH₂)aH whereina is 101 and b is
 56. 11. The composition of claim 1 wherein saidtherapeutic agent is a chemotherapeutic agent.
 12. The composition ofclaim 11 wherein said chemotherapeutic is a taxoid molecule.
 13. Thecomposition of claim 12 wherein said taxoid molecule is paclitaxel. 14.The composition of claim 1 wherein the particle size of said emulsion is10 to 500 nm.
 15. A pharmaceutical composition, comprising:α-tocopherol, one or more surfactants, and a therapeutic agent whereinsaid composition is in the form of a self-emulsifying drug deliverysystem and wherein said composition is substantially ethanol free. 16.The composition of claim 15 wherein said therapeutic agent is achemotherapeutic agent.
 17. The composition of claim 6 wherein saidchemotherapeutic agent is a taxoid molecule.
 18. The composition ofclaim 7 wherein said taxoid molecule is paclitaxel.
 19. The compositionof claim 15 wherein said surfactant is a vitamin E derivative.
 20. Thecomposition of claim 19 wherein said vitamin E derivative is an ester oran ether of vitamin E and polyethylene glycol.
 21. The composition ofclaim 19 wherein said vitamin E derivative is TPGS.
 22. The compositionof claim 21 wherein the ratio of α-tocopherol to TPGS is from about 1:1to about 10:1 w/w.
 23. The composition of claim 15 wherein the particlesize of said self-emulsifying drug delivery system is from about 10 toabout 500 nm.
 24. A method of making an emulsion, comprising: a)dissolving a therapeutic agent in ethanol to form a therapeutic agentsolution; b) adding α-tocopherol to said therapeutic agent solution toform an α-tocopherol therapeutic agent solution; c) removing saidethanol from said α-tocopherol therapeutic agent solution to reduce theethanol concentration to less than 0.3% therein; d) blending saidsubstantially ethanol-free therapeutic agent solution with a surfactantto form a pre-emulsion; and e) homogenizing said pre-emulsion to form anemulsion.